THURSDAY, Dec. 13 (HealthDay News) -- As the U.S. Supreme Court prepares to enter the debate about gay marriage, a new study suggests that being in a legally recognized relationship of any kind may reduce feelings of nervousness, hopelessness and depression.

"We have established that there is a fundamental association between having a legal relationship and greater psychological health," said study author Richard Wight, an associate researcher in the department of community health sciences at the University of California, Los Angeles, School of Public Health.

Wight noted, however, that to reap the psychological benefits of a legally recognized relationship, marriage does not seem to be necessary. "Same-sex marriage is a somewhat better predictor of psychological health, but there is no statistical difference between those who are married and those who are in registered domestic partnerships," he said.

For some gay couples, Wight said achieving marital status feels like being a pioneer, breaking new ground and establishing a sense of equality for others. "For heterosexual couples, the rationale for marriage is broadly more economic resources, acknowledgment of the relationship and integration into the community," he said. "For same-sex couples, it's all that, plus it's reducing the stigmatization [from society]."

In November, Maine, Maryland and Washington became the first states to approve gay marriage at the ballot box. Six other states and the District of Columbia have authorized gay marriage through judicial rulings and legislation. The U.S. Supreme Court is set to rule next year on the constitutionality of the 1996 federal Defense of Marriage Act and California's Proposition 8.

In California, same-sex marriage was allowed in June 2008, but Proposition 8 overturned the right five months later. In 2010, the proposition was overturned by a U.S. District Court. As a result, there was a short window during which same-sex couples could be married in the state.

Since 2000, same-sex couples in California have been able to establish their relationship as registered domestic partnerships.

The new study, published online Dec. 13 in the American Journal of Public Health, used data from the 2009 California Health Interview Survey, which reached over 47,000 adults aged 70 and younger.

The respondents were asked whether they consider themselves to be straight, heterosexual, gay, lesbian, homosexual or bisexual. They were also asked how often in the last 30 days (on a scale of 0 to 4) they felt nervous, hopeless, restless or fidgety; so depressed that nothing could cheer them up; everything was an effort; and worthless.

Those who identified themselves as gay were also asked whether they were legally registered as a domestic partner or married in California with someone of the same sex. Heterosexuals were asked whether they were married, living with a partner in a marriage-like relationship, widowed, divorced, separated or never married. Factors such as gender, ethnicity, age, education, employment status, health insurance status, health and household income were accounted for to ensure they did not interfere with the study results.

The researchers found that psychological distress was lower among people in a legally recognized relationship, whether gay or straight.

Those in same-sex relationships that were legally recognized -- either as marriage or as a registered domestic partnership -- also revealed less psychological distress. Among heterosexuals, those who were married showed significantly less distress than did those who were not.

The study authors wrote that while they were unable to prove it with this study, they believe mental health may improve as gay people have access to relationships that provide higher degrees of social and legal recognition. Wight explained that's why he believes same-sex marriage is a public health issue.

Markie Blumer, an assistant professor in the marriage and family therapy department at the University of Nevada, in Las Vegas, agreed. "Any time we have people who are stigmatized and feel not supported by the larger society, it can become a public health issue," she said. "It's complicated. Marriage may be just one part of it; people may be gay or lesbian, and also an ethnic minority, and maybe also a religious minority, depending on where they live."

Blumer thinks reducing psychological distress in people who are not heterosexual goes beyond the question of marriage.

"It's not the answer but it's a step in the right direction," she said. "You'd feel supported in your relationship by the general public and have way more legal rights. If the barriers of same-sex marriage were removed, people would be on more solid ground."

The study found an association between being in a legally recognized relationship and having better mental health, but it didn't prove cause-and-effect.